This invention relates to polyester filaments. In one of its aspects this invention relates to melt spinning of polyester filaments. In another of its aspects this invention relates to yarn produced from a multiplicity of filaments and fabric produced from this yarn.
In preferred aspects of the invention, it relates to the manufacture of polyester yarn which can be made into a double knit fabric which does not exhibit sparkle highlights when exposed to sunlight or other intense light.
In the recent past, polyester yarns have become widely used in apparel fabrics for women's wear such as pantsuits, blouses, skirts, dresses, coats and other items of apparel. Polyester yarn fabrics have also been adapted for use in men's wear for double knit suits, trousers, and the like. These polyester fabrics have demonstrated wash and wear characteristics which make them most desirable. The fabrics are also quite durable as compared to some of the natural fibers.
There has, however, been a major objection to fabrics made from polyester yarns when used in men's wear. This objection is based on the fact that polyester yarns generally produce sparkle highlights when exposed to sunlight or other intense light. A more desirable fabric for men's wear would not exhibit the sparkle or sparkle highlights but could exhibit a sheen which does not glitter.
Synthetic fibers can be made in a wide variety of individual filament cross-sections such as round, flat, trilobal, Y-shaped, octalobal, and the like. Most of the yarns which exhibit sparkle highlights are made from filaments that are round or substantially round. The reflection of light from these filaments causes the sparkle highlights. One method used for reducing the sparkle highlights is to use an octalobal fiber, i.e., a fiber having eight lobes, in the production of yarns. The octalobal fibers are usually made with a spinneret in which each hole has a cross-section having eight wings emanating from a center point. These eight wings may have different configurations at the ends of the wings such as a round lobe, but still upon extrusion the polymer swells to cause the wing extrudate to come together to form an octalobal fiber. Normally a spinneret will have 34 of these winged holes, but can have any number desired.
The spinneret described above for producing an octalobal fiber is expensive to construct and has operational shortcomings. During the spinning of fibers it often becomes necessary to wipe the spinneret to remove charred polymer. This is usually done with an implement called a wipe stick that is made from bronze and is substantially in the shape of a chisel. With the type of hole configuration in which the wings extend radially from the center, the wings are usually about 0.003" wide. Carbon particles frequently become lodged in the wings so that the fiber extruding from the hole in the spinneret is distorted. Carbon particles also frequently substantially plug the opening.
To overcome the disadvantages discussed above, it was determined to make and octalobal fiber by using an array of nine round holes arranged so that there was one center hole with eight equally spaced holes around the center hole for each of 34 fibers extruded from the spinneret. Upon extrusion it would be expected that the polymer from each of the nine holes would coalesce to form an individual filament. The use of such an arrangement to make a filament is not new in the art. Surprisingly, however, upon using such an array of nine holes within certain limitations of size, the fiber produced was not octalobal but was C-shaped. Furthermore, it was observed that the C-shaped fibers exhibit some flat spots. Happily, upon subsequent draw texturing of yarn made from the C-shaped fibers it was discovered that fabric made from these yarns exhibited the non-glitter or sheen when viewed in the sunlight that makes octalobal filaments particularly valuable. The spinneret used in producing the C-shaped fibers is economical to manufacture and does not have the plugging and contamination drawbacks of the eight winged type configuration.
It is therefore an object of this invention to provide a method for producing C-shaped fibers of polyester. It is also an object of this invention to provide C-shaped fibers of polyester produced by this method, to combine these fibers into yarns, and to produce fabric from the yarn which exhibits non-glitter characteristics. It is also an object of this invention to provide a method for producing fibers using an economical spinneret. It is another object of this invention to provide a method for producing fibers using a spinneret that has a minimum of plugging and contamination problems.
Other aspects, objects, and the various advantages of this invention will become apparent upon studying this specification, the drawing, and the appended claims.